During daylight hours, the driver of a vehicle is able to readily detect and recognize objects that would be difficult or impossible to detect or recognize at night. For example, assume that a deer wanders into the road approximately 500 meters ahead of the vehicle. If this scenario occurs in the middle of a sunny day, the driver will not only be able to detect the fact that something is present ahead, but will readily recognize that it is a deer. On the other hand, if this same scenario occurs at night, particularly when the only illumination is from the headlights of the vehicle, the driver will not be able to detect that anything is there, much less recognize that it is a deer, because the deer will be beyond the range of the headlights. Moreover, by the time the driver does detect that something is in the road, and well before the driver can recognize what it is, the driver will be much closer to the deer than would be the case during daylight hours. Accordingly, the risk of a resulting accident is much higher at night than during the day.
Consequently, in order to supplement the natural vision of a driver, and thus reduce the risk of accidents, night vision systems have been developed for vehicles, including automobiles sold in the consumer market. Typical night vision systems include an infrared camera unit, which gathers information regarding the scene in front of the vehicle, mounted in the grill of the vehicle and a head-up display, which projects an image derived from information provided by the camera unit onto the windshield, mounted in the vehicle's dashboard.
In these systems, the image projected generally has field of view of approximately twelve degrees horizontal by four degrees vertical. While this field of view is acceptable for driving on a straight, level road, the field of view is inadequate when, for example, negotiating curves, where it would be helpful to observe into the turn, and/or climbing hills, where it would be helpful to observe the top of the hill while cresting it. Unfortunately, a simple solution to this limited field view problem is not readily available.
The most straightforward solution would be to increase the size of the image projected onto the windshield to display a larger field of view. However, the space in which the head-up display must fit within the dashboard severely limits such efforts.
Another solution is to minify the image projected onto the windshield, thereby projecting more of the scene in front of the vehicle onto the same area of the windshield. Minification, however, decreases the size of the objects that the driver sees in the projected image relative to the actual size of the objects and, hence, reduces the driver's ability to perceive the range of objects seen in the image.